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Death to Cookies Konstantin Haase @konstantinhaase

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story time

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once upon a time

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Recipetastic™

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Bob Alice

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Bob Alice

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Bob Alice Eve

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Bob Alice Mallet

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problem solved

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POST /login HTTP/1.1 Host: www.recipetast.ic Content-Length: 44 [email protected]& password=st0p%20Motion

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HTTP/1.1 200 OK Content-Type: text/html Set-Cookie: user=bob ...

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GET / HTTP/1.1 Host: www.recipetast.ic Cookie: user=bob

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Guessing

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HTTP/1.1 200 OK Content-Type: text/html Set-Cookie: user=bob Set-Cookie: pwd=... ...

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GET / HTTP/1.1 Host: www.recipetast.ic Cookie: user=bob,pwd=...

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GET / HTTP/1.1 Host: www.recipetast.ic Cookie: user=bob,pwd=... Basic Auth, just with cookies

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HTTP/1.1 200 OK Content-Type: text/html Set-Cookie: user=bob Set-Cookie: token=... ...

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XSS Cross Site Scripting

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can read cookie and send it somewhere

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HTTP/1.1 200 OK Content-Type: text/html Set-Cookie: user=bob; HttpOnly ...

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can read (and write) recipes

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sanitize all user input

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Content Security Policy

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CSRF Cross Site Request Forgery

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Is this awesome, y/n?

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GET /create?… HTTP/1.1 Host: www.recipetast.ic Cookie: user=alice

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GET /create?… HTTP/1.1 Host: www.recipetast.ic Cookie: user=alice Deadly cookies!

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GET, HEAD, OPTIONS, TRACE PUT, DELETE, LINK, UNLINK POST, PATCH

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1 2 PUT / 2 PUT / 2 Repeatable! :) State change! :( Deterministic! :) https://speakerdeck.com/rkh/we-dont-know-http

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GET, HEAD, OPTIONS, TRACE PUT, DELETE, LINK, UNLINK POST, PATCH

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POST /create HTTP/1.1 Host: www.recipetast.ic Cookie: user=alice ...

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POST /create HTTP/1.1 Host: www.recipetast.ic Cookie: user=alice ... Deadly cookies!

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POST /create HTTP/1.1 Host: www.recipetast.ic Referer: http://awesome- website.com/ Cookie: user=alice

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POST /create HTTP/1.1 Host: www.recipetast.ic Referer: http://awesome- website.com/ Cookie: user=alice [sic]

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Referer is not set for FTP or HTTPS referrers

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Referer can be spoofed by outdated flash plugin

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POST /create HTTP/1.1 Host: www.recipetast.ic Origin: http://awesome- website.com Cookie: user=alice

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Not supported by older browsers

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Origin can probably be spoofed by outdated flash plugin

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HTTP/1.1 200 OK Content-Type: text/html Set-Cookie: csrf_token=XXX

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Cheating Same Origin

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HTTP/1.1 200 OK Content-Type: application/json

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An attacker could just load it, right?

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AJAX can only load from the same origin (or CORS)

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seems harmless

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In JavaScript, you can override the array constructor.

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https://github.com/rkh/json-csrf

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Never serve JSON that has an array at top level (or don’t use cookies)

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VBScript did not fully implement Same Origin

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Block Internet Explorer before IE9

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Block Internet Explorer before IE9

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require CSRF token for all AJAX requests

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Are we doing good so far?

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Can we trust a cookie?

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DNS cache poisoning

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Can we trust the browser?

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Can we trust browser plugins?

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Signed Cookies

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Encrypted Cookies

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Eaves- dropping

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encrypting cookies does not help

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attacker cannot parse cookie from stream

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Or can they?

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BEAST Browser Exploit Against SSL/ TLS

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decrypts TLS 1.0 streams via injected JavaScript

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fixed in TLS 1.1

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force recent browser

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don’t allow TLS 1.0

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CRIME Compression Ratio Info-leak Made Easy

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SSL has built-in compression

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GET /?user=alice HTTP/1.1 Host: www.recipetast.ic Cookie: user=bob GET /?user=bob HTTP/1.1 Host: www.recipetast.ic Cookie: user=bob better compression

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update your browser

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turn off SSL compression

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append random number of bytes to response

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BREACH Browser Reconnaissance and Exfiltration via Adaptive Compression of Hypertext

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like CRIME, but for the response

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attack the CSRF token, not the cookie

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inject something in the response http://www.recipetast.ic/search?q=XXX

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mask CSRF tokens differently in every response (Rails PR pending)

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don’t use CSRF tokens

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Do you think about all this when you build an app?

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Next attack vector around the corner?

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Alternatives

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IP address

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Session ID in URL

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Custom Authorization header

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Store value in Local Storage

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Needs JavaScript :(

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Works well with PJAX/ Turbo Links like setups

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New Browser Concepts?

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@konstantinhaase [email protected] rkh.im